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got a little further in xml chapter

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Mark Pilgrim
2009-05-17 00:41:29 -04:00
parent 95477d5e71
commit 9934530765
4 changed files with 81 additions and 3 deletions
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dip3.css
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@@ -35,6 +35,10 @@ Classname Legend
.q = "quote" = quote at beginning of each chapter
.f = "fancy" = first paragraph of each chapter (gets a fancy drop-cap)
.c = "centered" = centered footer text (also clears floats)
.s = "simple" =
.nm = "no mobile" = hide this section on mobile devices
.nd = "no decoration" = hide the widgets on this code block
.note = "note/caution/important" = indented block for tips/gotchas/language comparisons
.baa = "best available ampersand" = wrapper block for ampersands
dip3.js
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@@ -11,7 +11,7 @@ $(document).ready(function() {
pre.addClass("code");
}
});
$("pre.code, pre.screen").each(function(i) {
$("pre.code:not(.nd), pre.screen:not(.nd)").each(function(i) {
this.id = "autopre" + i;
$(this).wrapInner('<div class=b></div>');
$(this).prepend('<div class=w>[<a class=toggle href="javascript:toggleCodeBlock(\'' + this.id + '\')">' + HS['visible'] + '</a>] [<a href="javascript:plainTextOnClick(\'' + this.id + '\')">open in new window</a>]</div>');
generators.html
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@@ -276,7 +276,7 @@ finally:
<ol>
<li>The <code>build_match_and_apply_functions()</code> function has not changed. You&#8217;re still using closures to build two functions dynamically that use variables defined in the outer function.
<li>Open the file that contains the pattern strings.
<li>Read through the file one line at a time, using the <code>for line in &lt;fileobject&gt;</code> idiom.
<li>Read through the file one line at a time, using the <code>for line in &lt;fileobject></code> idiom.
<li>Each line in the file really has three values, but they&#8217;re separated by whitespace (tabs or spaces, it makes no difference). To split it out, use the <code>split()</code> string method. The first argument to the <code>split()</code> method is <code>None</code>, which means &#8220;split on any whitespace (tabs or spaces, it makes no difference).&#8221; The second argument is <code>3</code>, which means &#8220;split on whitespace 3 times, then discard the rest of the line.&#8221; A line like <code>[sxz]$ $ es</code> will be broken up into the list <code>['[sxz]$', '$', 'es']</code>, which means that <var>pattern</var> will get <code>'[sxz]$'</code>, <var>search</var> will get <code>'$'</code>, and <var>replace</var> will get <code>'es'</code>. That&#8217;s a lot of power in one little line of code.
<li>Use a <code>try..finally</code> block to ensure the file object is closed.
</ol>
xml.html
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@@ -89,9 +89,83 @@ mark{display:inline}
&lt;/entry>
&lt;/feed></code></pre>
<h2 id=xml-intro>A 5-Minute Crash Course in XML</h2>
<p>If you already know about XML, you can skip this section.
<p>XML is a generalized way of describing hierarchical structured data. An XML <i>document</i> contains one or more <i>elements</i>, which are delimited by <i>start and end tags</i>. This is a complete (albeit boring) XML document:
<pre class=nd><code><a>&lt;foo> <span>&#x2460;</span></a>
<a>&lt;/foo> <span>&#x2461;</span></a></code></pre>
<ol>
<li>This is the <i>start tag</i> of the <code>foo</code> element.
<li>This is the matching <i>end tag</i> of the <code>foo</code> element. Like balancing parentheses in writing or mathematics or code, every start tag much be <i>closed</i> (matched) by a corresponding end tag.
</ol>
<p>Elements can be <i>nested</i>. An element <code>bar</code> inside an element <code>foo</code> is said to be a <i>subelement</i> or <i>child</i> of <code>foo</code>.
<pre class=nd><code>&lt;foo>
<mark>&lt;bar>&lt;/bar></mark>
&lt;/foo>
</code></pre>
<p>Elements can have <i>attributes</i>, which are name-value pairs. Attributes are listed within the start tag of an element. <i>Attribute names</i> can not be repeated on the same element (although they can appear on different elements). <i>Attribute values</i> must be quoted.
<pre class=nd><code><a>&lt;foo <mark>lang="en"</mark>> <span>&#x2460;</span></a>
<a> &lt;bar <mark>lang="fr"</mark>>&lt;/bar> <span>&#x2461;</span></a>
&lt;/foo>
</code></pre>
<ol>
<li>The <code>foo</code> element has one attribute, named <code>lang</code>. The value of its <code>lang</code> attribute is <code>en</code>.
<li>The <code>bar</code> element has one attribute, named <code>lang</code>. The value of its <code>lang</code> attribute is <code>fr</code>. This doesn&#8217;t conflict with the <code>foo</code> element in any way. Each element has its own set of attributes.
</ol>
<p>Elements can have <i>text content</i>.
<pre class=nd><code>&lt;foo lang="en">
&lt;bar lang="fr"><mark>PapayaWhip</mark>&lt;/bar>
&lt;/foo>
</code></pre>
<p>Elements that contain no text and no children are <i>empty</i>.
<pre class=nd><code>&lt;foo>&lt;/foo></code></pre>
<p>There is a shorthand for writing empty elements. By putting a <code>/</code> character in the start tag, you can skip the end tag altogther. The XML document in the previous example could be written like this instead:
<pre class=nd><code>&lt;foo<mark>/</mark>></code></pre>
<p>Like Python functions can be declared in different <i>modules</i>, XML elements can be declared in different <i>namespaces</i>. Namespaces usually look like URLs. You use an <code>xmlns</code> declaration to define a <i>default namespace</i>. A namespace declaration looks similar to an attribute, but it has a different purpose.
<pre class=nd><a><code>&lt;feed <mark>xmlns="http://www.w3.org/2005/Atom"</mark>> <span>&#x2460;</span></a>
<a> &lt;title>dive into mark&lt;/title> <span>&#x2461;</span></a>
&lt;/feed>
</code></pre>
<ol>
<li>The <code>feed</code> element is in the <code>http://www.w3.org/2005/Atom</code> namespace.
<li>The <code>title</code> element is also in the <code>http://www.w3.org/2005/Atom</code> namespace. The namespace declaration affects the element where it&#8217;s declared, plus all child elements.
</ol>
<p>You can also use an <code>xmlns:<var>prefix</var></code> declaration to define a namespace and associate it with a <i>prefix</i>. Then each element in that namespace must be explicitly declared with the prefix.
<pre class=nd><a><code>&lt;atom:feed <mark>xmlns:atom="http://www.w3.org/2005/Atom"</mark>> <span>&#x2460;</span></a>
<a> &lt;atom:title>dive into mark&lt;/atom:title> <span>&#x2461;</span></a>
&lt;/atom:feed>
</code></pre>
<ol>
<li>The <code>feed</code> element is in the <code>http://www.w3.org/2005/Atom</code> namespace.
<li>The <code>title</code> element is also in the <code>http://www.w3.org/2005/Atom</code> namespace.
</ol>
<p>As far as a namespace-aware XML parser is concerned, the previous two XML documents are <em>identical</em>. Namespace + element name = XML identity. Prefixes are irrelevant.
<h2 id=xml-structure>The Structure Of An Atom Feed</h2>
<p>FIXME
<p>Think of a weblog, or in fact any website with frequently updated content, like <a href=http://www.cnn.com/>CNN.com</a>. The site itself has a title (&#8220;CNN.com&#8221;), a subtitle (&#8220;Breaking News, U.S., World, Weather, Entertainment <i class=baa>&amp;</i> Video News&#8221;), a last-updated date (&#8220;updated 12:43 p.m. EDT, Sat May 16, 2009&#8221;), and a list of articles posted at different times. Each article also has a title, a first-published date (and maybe also a last-updated date, if they published a correction or fixed a typo), and a unique URL.
<p>The Atom syndication format is designed to capture all of this information in a standard format. My weblog and CNN.com are wildly different in design, scope, and audience, but they both have the same basic structure. CNN.com has a title; my blog has a title. CNN.com publishes articles; I publish articles.
<p>At the top level is the &#8220;root&#8221; element, which every Atom feed shares: the <code>&lt;feed></code> element in the Atom namespace (<code>http://www.w3.org/2005/Atom</code>). ... FIXME
<h2 id=xml-parse>Parsing XML</h2>